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The Plot

We're setting up a Kubernetes enviornment using RedHat's OCP.

The application that we've been given from our provider in the form of Helm charts and container images, provides a pod that basically just runs bash. From what I understand, their suggestion is that we do oc rsh <pod> do_something.sh for each of the somethings we want to do.

The Problem

I know enough about containers to be dangerous; I've never run them at anything even approaching scale. Like, I've started a couple hundred salt minions on my laptop using docker compose.

The approach of having a bash container just to rsh into and run commands in seems... silly.

The Question

Is there any non-trivial performance penalty, or any risk or downside at all, to running these commands as a Job in kubernetes instead? Something like

apiVersion: batch/v1 kind: Job metadata: name: something_doer spec: template: spec: containers: - name: something_doer image: that_bash_image:42 command: ["do_something.sh"] restartPolicy: Never backoffLimit: 5

Is there any reason why we would not want to launch this via kubectl apply (or oc apply)?

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I'd always, and I mean always suggest you use a bog standard Kubernetes resource over a specialized cli command of your k8s distribution.

  1. It is well known and understood.
  2. It is independent of the underlying implementation of the k8s cluster.
  3. In this case, a job creates more meaningful metrics. There is a difference between a failed job and a standard pod in a crash loop.
  4. It can be integrated into GitOps and the ecosystem (think helm, kustomize etc) much more easily.

As for performance penalties: There should only be a negligible time offset between transferring the kubernetes job and its execution and running a pod directly. Other than that, they use the same image and the same software, hence presumably the same memory and compute resources.

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